Stupid car design question: Why don't they build cars with the engine and such in the back of the car?

[gotsmack]

To start off. I want to say I know crap about cars.

I was driving my old Volvo the other day (which is RWD) and was wondering why the engine and stuff is in the front of the car. If it were in back I would have more weight in the rear and it would help when driving in snow and rain.

I also remember hearing that RWD platforms were more expensive to build and was wondering if the placement of the mechanical guts of the car in the front has anything to do with it.

Whats the abantage of having the engine in the front?

 

[RGUN]

Puts weight on the wheels that will be doing the steering and reduces the chances of spinning out. Look into early Porsche RR designs to see how long it took them to get a forgiving rear engine rear drive platform

 

[Hyperlite]

Weight balance. Conventionally, fuel tanks are in the rear, and in a vehicle where (as most are) production cost is more of a factor than design and fucntionality, it is much more simple to just put components where there is naturally space.

 

[996GT2]

Porsche is the only large manufacturer of RR cars currently (AFAIK), and it's taken many years of work to turn them into the machines they are today from the early tail-happy 911s. One of the benefits of an RR setup is improved weight distribution under braking, and if you look at some of the braking results from Porsche 911s with PCCB, they rival those of exotics like the Ferrari Enzo.

Rear wheel steering isn't really feasible unless it's used in conjunction with traditional front wheel steering (e.g. Nissan's HICAS). Even in those systems, the rear wheels only ever move a few degrees and don't do much of the cornering work. Imagine driving your car in reverse and trying to steer. Even tiny movements of the wheel can lead to large direction changes.

 

[Toastedlightly]

Corvair... need I say more?

 

[mwmorph]

Mid engine is less practical. To make a car Mid Engine Rear Wheel Drive(MR), you basically need it to be extremely long to have it be more than a 2 seater and pass collision testing.

Rear engine allows rear seats, but then comes the problem of snap oversteer, especially on wet or low traction surfaces. Snap oversteer is already a problem on MR cars, on RR, it's mandatory. For the regular(shitty) driver, oversteer is unwanted since to correct oversteer, it takes instinctively the opposite inputs to correct(eg. braking induces more oversteer). Snap oversteer is even more so unwanted, because thats when shit hits the fan, the car does a 180* rotation and unexperienced drivers die.

 

[LTC8K6]

Because of Ralph Nader re Corvair re we give away driver's licenses in America.

 

[compnovice]

Not sure, but wouldn't safety be one of the concerns? A head on collision is more dangerous that a rear ended one, and you would want more metal between you and the other car/divider etc. Basically a better crumple zone?

 

[jagec]

Originally posted by: compnovice
Not sure, but wouldn't safety be one of the concerns? A head on collision is more dangerous that a rear ended one, and you would want more metal between you and the other car/divider etc. Basically a better crumple zone?

MR/RR designs are about performance with no compromises. Exotics and supercars are almost exclusively MR, or at least RR. You don't buy a Ferrari, Lamborghini, Porsche, GT40, S7, Koenigsegg (man I'm never going to learn how to spell that without Google), McClaren, or CLK-GTR because they're safer than other cars....you buy them for the handling.

You don't really understand "low polar moment of inertia" until you drive a mid-engined car. A touch of initial understeer as it effortlessly begins to rotate, and then as rotation occurs and the car starts rounding the corner there's a "sweet spot" in the throttle range between power oversteer (too much throttle) and snap oversteer (too little throttle, causing weight to shift and rear wheels to effectively overbrake their available traction as the engine tries to slow them). It's actually not all that different from a go-kart. Tricky for an inexperienced driver (part of the reason that they end up stuffed full of electronic geegaws to keep hamfisted owners out of guardrails), but they corner like a dream in the hands of someone who knows what they're doing. Great braking and acceleration, too.

Yes, ironically enough, most of the cars with mid and rear mounted engines (and therefore less substance in front during a collision) are also those likely to collide at very high speeds if they do. I advise goosing the throttle and spinning the car around backwards just prior to impact

 

[imported_Truenofan]

then there's trunk space.....you dont get a whole lot in the front, if any. having the trunk in the rear of a car just offers more due to design.

 

[Wolfie]

Should we remember the pontiac fiero? I think it stood for fire. hehe All I know is I knew of three of my friends that had these, and all three strarted on fire at one time or another.

 

[Zenmervolt]

Originally posted by: jagec
You don't really understand "low polar moment of inertia" until you drive a mid-engined car. A touch of initial understeer as it effortlessly begins to rotate, and then as rotation occurs and the car starts rounding the corner there's a "sweet spot" in the throttle range between power oversteer (too much throttle) and snap oversteer (too little throttle, causing weight to shift and rear wheels to effectively overbrake their available traction as the engine tries to slow them). It's actually not all that different from a go-kart. Tricky for an inexperienced driver (part of the reason that they end up stuffed full of electronic geegaws to keep hamfisted owners out of guardrails), but they corner like a dream in the hands of someone who knows what they're doing. Great braking and acceleration, too.

Just to play devil's advocate, the F/R 944 series are damn fine handling cars. Of course, they use a rear-mounted transaxle and have 50/50 weight distribution still. Having driven both M/R cars and the 944/951 I have to say that there are convincing arguments for each setup. The higher polar inertia of the 944/951 means that the car can make almost any driver look like a hero; there's essentially nothing you can do to upset the balance. You lose the instantaneous turn-in of the mid-engine cars, but you can still hang right with them.

ZV

 

[Zenmervolt]

Originally posted by: Wolfie
Should we remember the pontiac fiero? I think it stood for fire. hehe All I know is I knew of three of my friends that had these, and all three strarted on fire at one time or another.

Meh, that's not really fair. The fires were due to a design flaw in the Iron Duke 4-cylinder. When GM built the Fiero, they quite literally dropped a FWD drivetrain and suspension into the middle of the Fiero. The early 4-cylinder cars even still had fully functional tie rods and steering joints at the rear, the factory just welded them solidly into place on the assembly line.

ZV

 

[fstime]

Originally posted by: Zenmervolt

Originally posted by: jagec
You don't really understand "low polar moment of inertia" until you drive a mid-engined car. A touch of initial understeer as it effortlessly begins to rotate, and then as rotation occurs and the car starts rounding the corner there's a "sweet spot" in the throttle range between power oversteer (too much throttle) and snap oversteer (too little throttle, causing weight to shift and rear wheels to effectively overbrake their available traction as the engine tries to slow them). It's actually not all that different from a go-kart. Tricky for an inexperienced driver (part of the reason that they end up stuffed full of electronic geegaws to keep hamfisted owners out of guardrails), but they corner like a dream in the hands of someone who knows what they're doing. Great braking and acceleration, too.

Just to play devil's advocate, the F/R 944 series are damn fine handling cars. Of course, they use a rear-mounted transaxle and have 50/50 weight distribution still. Having driven both M/R cars and the 944/951 I have to say that there are convincing arguments for each setup. The higher polar inertia of the 944/951 means that the car can make almost any driver look like a hero; there's essentially nothing you can do to upset the balance. You lose the instantaneous turn-in of the mid-engine cars, but you can still hang right with them.

ZV

I was under the impression that 50/50 weight distribution was a bunch of crap and just a marketing gimmick; and in fact, the optimal setup would be something like 42/58.

 

[Vic]

The original front engine/RWD designs had nothing to with safety (the original Model T's didn't even have front brakes). It was just the limitations of the existing technology. When Porsche designed the first Volkswagen in the '30s, with rear engine/RWD, they were hailed as engineering marvels.
Likewise, the current designs of front engine/FWD are due to technological limitations and practicality. It didn't take Ralph Nader to convince manufacturers that people would rather put their luggage in the trunk than in the front, and that they would rather not have the gas tanks in the front of the car. However, if the technology existed that manufacturers could somehow stuff the whole drivetrain underneath the rear seat (where the gas tank usually goes now in most cars), I guarantee you that they would.

 

[Zenmervolt]

Originally posted by: BouZouki

Originally posted by: Zenmervolt

Originally posted by: jagec
You don't really understand "low polar moment of inertia" until you drive a mid-engined car. A touch of initial understeer as it effortlessly begins to rotate, and then as rotation occurs and the car starts rounding the corner there's a "sweet spot" in the throttle range between power oversteer (too much throttle) and snap oversteer (too little throttle, causing weight to shift and rear wheels to effectively overbrake their available traction as the engine tries to slow them). It's actually not all that different from a go-kart. Tricky for an inexperienced driver (part of the reason that they end up stuffed full of electronic geegaws to keep hamfisted owners out of guardrails), but they corner like a dream in the hands of someone who knows what they're doing. Great braking and acceleration, too.

Just to play devil's advocate, the F/R 944 series are damn fine handling cars. Of course, they use a rear-mounted transaxle and have 50/50 weight distribution still. Having driven both M/R cars and the 944/951 I have to say that there are convincing arguments for each setup. The higher polar inertia of the 944/951 means that the car can make almost any driver look like a hero; there's essentially nothing you can do to upset the balance. You lose the instantaneous turn-in of the mid-engine cars, but you can still hang right with them.

ZV

I was under the impression that 50/50 weight distribution was a bunch of crap and just a marketing gimmick; and in fact, the optimal setup would be something like 42/58.

50/50 allows for the easiest tuning of handling and lends itself to stable, neutral, balance. 42/58 would be well into the realm of snap-oversteer which would start requiring some sophisticated suspension design to overcome. This is one reason that the 944 Turbo will blow the doors off an equivalent age 911 Turbo on the track, even though the 911 Turbo is lighter and has closer to 40/60 weight distribution.

A slight rear bias in static weight does help on the track to keep balance under breaking and to provide better traction on acceleration (assuming RWD), but this also assumes that the driver is comfortable with a car that can snap-oversteer and knows what not to do.

The 914 is actually slightly tail-heavy, and even that will snap around if you lift throttle too fast in the middle of a corner. The 944/951, however, is much less prone to snap-oversteer because of less weight to the rear of the car. A car with 50/50 weight distribution will "feel" better and will be easier to drive at 10/10ths than a car with 45/55 or 40/60 even if the latter car may be very slightly faster in the hands of a supreme expert driver.

So, long explanation short, a slight rear weight bias is better for absolute highest potential handling, but 50/50 is best for making the limit of handling safely approachable by average to pretty-good drivers.

ZV

 

[jagec]

Originally posted by: Zenmervolt
A slight rear bias in static weight does help on the track to keep balance under breaking and to provide better traction on acceleration (assuming RWD), but this also assumes that the driver is comfortable with a car that can snap-oversteer and knows what not to do.

ZV

And to think that you're an elite member...you ought to be ashamed of yourself!

 

[Zenmervolt]

Originally posted by: jagec

Originally posted by: Zenmervolt
A slight rear bias in static weight does help on the track to keep balance under breaking and to provide better traction on acceleration (assuming RWD), but this also assumes that the driver is comfortable with a car that can snap-oversteer and knows what not to do.

ZV

And to think that you're an elite member...you ought to be ashamed of yourself!

I got 4 hours of sleep last night, even with the time change. Gimme a brake.

ZV

 

[exdeath]

Originally posted by: jagec

Originally posted by: compnovice
Not sure, but wouldn't safety be one of the concerns? A head on collision is more dangerous that a rear ended one, and you would want more metal between you and the other car/divider etc. Basically a better crumple zone?

MR/RR designs are about performance with no compromises. Exotics and supercars are almost exclusively MR, or at least RR. You don't buy a Ferrari, Lamborghini, Porsche, GT40, S7, Koenigsegg (man I'm never going to learn how to spell that without Google), McClaren, or CLK-GTR because they're safer than other cars....you buy them for the handling.

You don't really understand "low polar moment of inertia" until you drive a mid-engined car. A touch of initial understeer as it effortlessly begins to rotate, and then as rotation occurs and the car starts rounding the corner there's a "sweet spot" in the throttle range between power oversteer (too much throttle) and snap oversteer (too little throttle, causing weight to shift and rear wheels to effectively overbrake their available traction as the engine tries to slow them). It's actually not all that different from a go-kart. Tricky for an inexperienced driver (part of the reason that they end up stuffed full of electronic geegaws to keep hamfisted owners out of guardrails), but they corner like a dream in the hands of someone who knows what they're doing. Great braking and acceleration, too.

Yes, ironically enough, most of the cars with mid and rear mounted engines (and therefore less substance in front during a collision) are also those likely to collide at very high speeds if they do. I advise goosing the throttle and spinning the car around backwards just prior to impact

Sounds like an experienced MR2 owner

 

[Demon-Xanth]

Front engine allows the components that are hot to get good airflow, as well as in an impact, not crush the occupants. With rear engine, cooling becomes more difficult. Engine installation is also easier in a front engine car as you just drop the engine in through the hood. A front engine car is also more forgiving, especially for inexperienced drivers as a rear engine can whip around easier. Trunk space is also an issue, as people want all their crap behind them.

It's not one major reason, but a lot of little reasons that can be worked around if you're willing to make compromises.

 

[exdeath]

Originally posted by: gotsmack
To start off. I want to say I know crap about cars.

I was driving my old Volvo the other day (which is RWD) and was wondering why the engine and stuff is in the front of the car. If it were in back I would have more weight in the rear and it would help when driving in snow and rain.

I also remember hearing that RWD platforms were more expensive to build and was wondering if the placement of the mechanical guts of the car in the front has anything to do with it.

Whats the abantage of having the engine in the front?

Some other possible reasons, just a few things that I can think off of the top of my head:

Maintenance - ease of accessibility for common repairs; though a good mid engine design will be set up so the while engine can drop out very quickly. Still though the idea of "pulling out an engine" to replace an alternator sounds more complicated and expensive to people even if it only takes 10 mins to unbolt the engine cradle and harness and lift the car.

Cooling system - reliability and complexity in either having a remote radiator or getting cool air to the radiators.

Inertial balance - anytime you change the acceleration of a mass with uneven weight distribution, the heavier end goes first as it carries more inertia and is less effected by the resisting forces (same reason a throwing knife weight is biased toward the blade end or the reason a bullet yaws when it hits an abrupt change in medium density, probably the reason bread always lands gooey side down when you spread something on it, etc). In a rear engine layout, this makes the car tail happy as the heavy rear end wants to lead around corners. In a mid engine car, there is NO resistance to rotation since the mass is in the center, and the car is extremely sensitive to throttle and traction conditions.

Practical - mid engine nearly always means two seater and no trunk space (relative to other vehicles).

Cargo space - putting the engine between the driver seat and the rear wheels means pushing the driver compartment forward to make room for the engine. Also what was once overlapped under the center console (transmission) now occupied space of its own under the rear trunk. That means that not only do you have less space in the rear due to the engine and drive train components, but the room up front you naturally think would be freed up without an engine, is also reduced.

Visibility - small rear window and large B pillars are almost universal on every mid engine car out there. The B pillars have to be wide enough to match up with the width of the cover over the engine bay. Well they don't have to, but most designs for aesthetic reasons, even if the window drops straight down at the front of the engine, the pillars slope outward coming to a taper near the rear of the engine.

Convertibles - to complicate all the above space constraint issues, now add a convertible top that has to go somewhere.

 

[nakedfrog]

One of the world's most popular cars is a rear engine RWD setup, but they finally quit making them altogether in 2003

 

[exdeath]

Beetle? But the new ones were FWD.

 

[nakedfrog]

Originally posted by: exdeath
Beetle? But the new ones were FWD.

They kept making the originals south of the border up until 2003.

 

[Thump553]

I owned a Beetle and drove a Corvair as a kid (drugstore delivery). The Corvair's downfall was that it was very sporty and seemed very stable-to track like a railroad train-right up until the moment you could tuck the rear wheel under itself by cornering too hard. I came close to this situation several times just driving around town (probably 30-40 mph max). The Beetle handled fine, but it had barely any luggage space up front and the rear engine compartment was so small that the engine was hard for clumsy-handed people like me to work on. You could see the nuts, etc. but it would be a bear to get a wrench on them. My Beetle was also of the era that had the battery inside the passenger compartment-a very dangerous location in the event of an accident.

Frankly having lived most of my life in snowy areas, I think front wheel drive/front transverse mounted engine is the best thing since sliced bread. No way I would go back to rear wheel drive.